#! python3
import requests,os,bs4

url='http://xkcd.com'
os.makedirs('xkcd',exist_ok=True)
while not url.endswith("#"):
    # TODO: Download the page.
    print('Downloading %s...' %url)
    res=requests.get(url)
    res.raise_for_status()
    soup=bs4.BeautifulSoup(res.text)
    # TODO: Find the URL of the comic image.
    comicElem=soup.select('#comic img')
    if comicElem == []:
        print('Could not find comic image.')
    else:
        comicUrl = 'http:'+ comicElem[0].get('src')
        # Download the image.
        print('Downloading image %s...' % (comicUrl))
        res = requests.get(comicUrl)
        res.raise_for_status()
    # TODO: Save the image to ./xkcd.
    imageFile = open(os.path.join('xkcd', os.path.basename(comicUrl)), 'wb')
    for chunk in res.iter_content(100000):
        imageFile.write(chunk)
    imageFile.close()
    # TODO: Get the Prev button's url.
    prevLink = soup.select('a[rel="prev"]')[0]
    url = 'http://xkcd.com' + prevLink.get('href')
print('Done.')